1. Field of the Invention
The present invention relates to a map information processing apparatus that acquires map information from outside the map information processing apparatus, carries out route determination, and displays route determination results on a map, and a map information transmission center that provides map information for the map information processing apparatus.
2. Description of Related Art
As shown in Japanese patent application No. 2000-121,371, for example, in order to reduce the amount of map information data to be transmitted, a prior art map information processing apparatus limits transmission of map information to the one about a predetermined region. The prior art map information processing apparatus limits transmission of map information to information about a predetermined region by referring to a past use history and automatically acquires updated map data associated with the region whose map information needs to be kept up to date. Such a limited region can be defined by a plurality of unit regions, which are called meshes defined in two dimensions, as shown in FIG. 46. For example, the region consists of a plurality of meshes enclosed by a heavy line of FIG. 46. The region can be determined according to one or more vehicle positions (plot points) acquired based on the use history. As an alternative, each mesh is ranked based on the number of plot points included therein, and meshes ranked in the top N (N is a predetermined number) are selected as the region. The determination of such a limited region can be carried out by either the vehicle equipped with the map information processing apparatus or a map providing center (map information transmission center) that provides map information. The map providing center delivers the map information data about the limited region to the map information processing apparatus of the vehicle, and the map information processing apparatus updates map information stored therein based on the map information data transmitted thereto from the map providing center, carries out route determination and so on based on the updated map information, and displays route determination results on a map transmitted thereto. The determination of such a limited region can be carried out by either the vehicle equipped with the map information processing apparatus or a map providing center (map information transmission center) that provides map information. The map providing center delivers the map information data about the limited region to the map information processing apparatus of the vehicle, and the map information processing apparatus updates map information stored therein based on the map information data transmitted thereto from the map providing center, carries out route determination and so on based on the updated map information, and displays route determination results on a map transmitted thereto.
In a system including a prior art map information processing apparatus constructed as mentioned above, map information for route determination and map information for route determination result providing are determined in a similar way based on the limitation of a region whose map information is to be transmitted to the map information processing apparatus. As a result, when the region whose map information is to be transmitted to the map information processing apparatus is reduced to a small region in order to reduce the amount of data transmitted, there is a possibility that when performing route determination the frequency of requiring the map information about regions whose map information has not been transmitted to the map information processing apparatus is increased and therefore the route determination cannot be carried out. Although the limitation of a region whose map information is to be transmitted to the map information processing apparatus can be relaxed to solve this problem, the reduction in the amount of data to be transmitted cannot be accomplished by using this method.
The present invention is proposed to solve the above-mentioned problems, and it is therefore an object of the present invention to provide a map information processing apparatus that can carry out route determination at all times.
It is another object of the present invention to provide a map information transmission center that enables a map information processing apparatus to carry out route determination at all times without increasing the amount of data transmitted to the map information processing apparatus.
In accordance with an aspect of the present invention, there is provided a map information processing apparatus including a route determination unit for determining a route between two arbitrary points by using map information for route determination having one or more levels of hierarchy, a route determination result providing unit for providing route determination results obtained by the route determination unit by using map information for route determination result providing, and an external map information acquiring unit for, when acquiring map information about a predetermined region from outside the map information processing apparatus, acquiring map information for route determination result providing having information about a region of an arbitrary size including the predetermined region, and map information for route determination about at least one unit region including the predetermined region, which is included in map information for route determination at a top of the hierarchy, and map information for route determination about all unit regions that exist at lower levels of the hierarchy than the unit region including the predetermined region. As a result, the map information processing apparatus can carry out route determination at all times without any increase in the amount of transmission data.
In accordance with another aspect of the present invention, there is provided a map information processing apparatus including a route determination unit for determining a route between two arbitrary points by using map information for route determination having one or more levels of hierarchy, a route determination result providing unit for providing route determination results obtained by the route determination unit by using map information for route determination result providing, a map information storage unit for storing the map information for route determination and the map information for route determination result providing, a map information correction unit for making a correction to map information including information about a predetermined region, which is included in the map information held by the map information storage unit, and an external map information acquiring unit for, when acquiring correction map information used for making a correction to the map information including the information about the predetermined region from outside the map information processing apparatus, acquiring map information for route determination result providing having information about a region of an arbitrary size including the predetermined region, and map information for route determination about at least one unit region including the predetermined region, which is included in map information for route determination in a top of the hierarchy, and map information for route determination about all unit regions that exist at lower levels of the hierarchy than the unit region including the predetermined region. As a result, the map information processing apparatus can reduce the amount of data acquired from outside the map information processing apparatus.
In accordance with a further aspect of the present invention, there is provided a map information transmission center including a map information storage unit for storing map information for route determination having one or more levels of hierarchy and map information for route determination result providing, and a map request processing unit for when receiving a request for map information about a predetermined region from outside the map information transmission center, reading map information for route determination result providing having information about a region of an arbitrary size including the predetermined region, and map information for route determination about at least one unit region including the predetermined region, which is included in map information for route determination at a top of the hierarchy, and map information for route determination about all unit regions that exist at lower levels of the hierarchy than the unit region from the map information storage unit, and for delivering those read pieces of map information to an information providing unit for providing map information for outside the map information transmission center. As a result, the map information transmission center enables external equipment to carry out route determination at all times without any increase in the amount of data required for route determination and route determination result providing.
In accordance with another aspect of the present invention, there is provided a map information transmission center including a map information storage unit for storing correction map information used for making a correction to one or more versions of map information each including map information for route determination having one or more levels of hierarchy and map information for route determination result providing, a map request processing unit for when receiving a request for map information about a predetermined region from outside the map information transmission center, reading both correction map information used for making a correction to map information for route determination result providing having information about a region of an arbitrary size including the predetermined region and correction map information used for making a correction to both map information for route determination about at least one unit region including the predetermined region, which is included in map information for route determination at a top of the hierarchy, and map information for route determination about all unit regions that exist at lower levels of the hierarchy than the unit region from the map information storage unit, and for delivering those read pieces of correction map information to an information providing unit for providing map information for outside the map information transmission center. As a result, the map information transmission center can reduce the amount of data provided to outside the map information transmission center.